1. Field of the Invention
The present invention relates to a method and apparatus for releasably securing a first surface in a sealed relationship with a second surface. More particularly, the present invention provides a method and apparatus for releasably securing the cover of a processing chamber in a sealed relationship with the chamber walls and for regulating high end pressure within the chamber. More particularly still, the present invention provides a pressure responsive fastener which operates as a chamber cover restraint and as a pressure relief mechanism in the event of a sudden increase in pressure within the chamber.
2. Background of the Related Art
Fabrication of integrated circuit structures on semiconductor substrates is generally carried out in processing chambers which typically operate at low pressures. One example of a low pressure process is the deposition of a dielectric film in a subatmospheric chemical deposition (SACVD) chamber. Typically, a processing chamber includes a chamber wall having a lid hingedly attached to the upper edge of the chamber walls. The hinged lid enables access to the chamber components to facilitate repair and cleaning of the chamber, while preserving alignment of the lid with the sealing surfaces of the chamber. The lid of the chamber is lowered onto the chamber walls and the pressure within the chamber is lowered by various types of vacuum pumps. The chamber lid forms a sealed relationship with the chamber walls under the vacuum pressure within the chamber to form an evacuable enclosure.
Substrate processing within a system is typically carried out without interruption for several days before routine maintenance and cleaning of the system must be performed. The lid of the chamber in the system is secured in sealed, abutting engagement with the chamber walls to provide a vacuum environment that can be pumped down so that the fabrication processes can be carried out at a subatmospheric pressure. Clamping members are typically employed to fasten the lid in abutting engagement with the chamber walls, while permitting the lid to be periodically opened to provide access to the chamber.
The mating surfaces of the cover and chamber walls are typically prepared with machined surfaces with tight tolerances to form a seal around the perimeter of the cover. An O-ring type gasket is commonly disposed between the opposing lid and chamber sealing surfaces to provide an airtight seal despite minor variations in the opposing surfaces. The vacuum pressure within the chamber acts on the lid to pull the lid downward against the chamber walls and O-ring disposed therebetween to form an airtight seal between the lid and chamber walls and prevent air from leaking into the processing chamber.
The processing environment typically existing within the chamber is maintained at low pressure and returned to atmosphere prior to routine maintenance. However, pressure within the chamber may rise to levels at or above atmospheric pressure. It would be desirable to controllably release pressure within the chamber if the pressure reaches an undesirable level. Clamps presently used to secure the lid to the chamber walls are not pressure responsive and cannot vent the chamber should the pressure within the chamber suddenly increase. Presently available fasteners used in subatmospheric applications must be checked for any damage and the springs or the fasteners replaced if a pressure excursion occurs. Inspection and repair are time consuming and costly because the system must be shut down, inspection and repair completed, and then the system must again be pumped down to the processing pressure.
In addition to functional limitations, clamps presently available are costly and difficult to manufacture. One example of a clamp utilizes a tension spring having a first end secured to the exterior of the chamber wall and a second end having a clasp that is connectable with a hook located on the lid. Regardless of the exact means for securing the spring ends, it should be noted that the spring must be maintained in tension during normal operation of the chamber in order to maintain the lid in sealed relationship with the chamber walls. The tension placed on the spring manually by the operator each time the cover is closed and during operation compromises the integrity of the springs. An increase in chamber pressure typically results in plastic deformation of the springs thereby requiring replacement. Furthermore, the repeated application and removal of tension on the spring over a period of time, i.e. repeated opening of the chamber, may compromise the integrity of the spring.
Therefore, there exits a need for a pressure responsive fastener for a semiconductor processing chamber which facilitates release of pressure within the chamber to prevent damage to the chamber or components within the chamber. After the pressure has been released, the fastener would preferably return the lid to the sealed position so that processing may resume. It would be desirable to have a fastener that is simple to construct and operate, small, light weight and inexpensive to manufacture. Furthermore, it would be desirable to have a clamp with no moving parts and made from materials that will not release contaminants into a clean room environment.